Colour never plays a part in choosing fish for me, fish behaviour is what attracts me most and seconded by rarity in the hobby. A lot of my fish are the drab browns, greens and greys assosiated with predatory fish which would not appeal to fish keepers who are more familiar with brightly coloured community fish and Cichlids. That said i do keep a few fish with stunning colouration such as my jardini arowana, peacock bass and dwarf snakeheads, but the fact they are colourfull is just a lucky coincidense.
I love the finnage on many fish and how it varies. Possibly what attracted me to the eupterus types was the finnage. The wonderful patterning on some is a factor and for older fish I buy the character comes into play. Hard to discern the character of smaller young fish when they're in a tank with 50 others. Also get some that are rescues, such as both the male bettas. But I did get Vanity (one of my female bettas) because of her colouration. I'd always wanted a green girl and she is georgeous.